The present invention relates to a fuel injection type internal combustion engine.
An internal combustion engine of a gasoline injection type has been proposed in which a fuel injector is provided for each cylinder, and the fuel is injected from each of the fuel injectors into the intake ports of the corresponding cylinders. This engine has an advantage in that the distribution of fuel to each cylinder becomes uniform. However, in this engine, there is a problem in that the atomization of the fuel fed into the combustion chambers from the fuel injectors is not fully promoted, and that the provision of a plurality of the fuel injectors is necessary. In order to eliminate the above-mentioned problem, another internal combustion engine has been proposed, in which a single fuel injector is arranged upstream of the throttle valve in the intake duct which is connected to the collecting portion of the intake manifold. This engine has advantages in that, since the fuel injected from the fuel injector impinges upon the throttle valve, the atomization of the fuel is promoted, and that the vaporization of the fuel is promoted during the time the fuel flows within the intake manifold. However, in this engine, there are problems in that, since the amount of the fuel distributed to each cylinder varies between the cylinders in accordance with changes in the opening degree of the throttle valve, the irregularity of the air-fuel ratio in each cylinder becomes large, and that, since it takes long time until the fuel injected from the fuel injector reaches the combustion chambers, the time lag of the responsiveness of the controlling operation of the fuel injection is increased.
In addition, a further internal combustion engine has been proposed, in which a single fuel injector is so arranged that the fuel is injected into the collecting portion of the intake manifold from the fuel injector. This engine has an advantage in that the responsiveness of the controlling operation of the fuel injection is improved as compared with the case wherein the fuel injector is arranged at a position located upstream of the throttle valve as mentioned above. However, in this engine, the atomization of the fuel injected from the fuel injector is not fully promoted as compared with the case wherein the fuel injector is arranged at a position located upstream of the throttle valve and, in addition, since the slight changes in the location of the fuel injector and in the injecting direction of the fuel injector cause a great change in the distribution of the fuel to each cylinder, it is difficult to practically find the optimum location and the optimum injecting direction of the fuel injector.